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The Greeks dubbed them “river horses,” and for years, archeologists and biologists agreed that they were probably (evolutionary) cousins to modern-day pigs, but recently, DNA analysis has shown that hippos have a much stranger history than that. Descendants of a 60-million-year-old ancestor that’s long since gone extinct, hippos’ closest living relatives don’t live nearby and don’t look much like them (and presumably never call): they’re whales.

It makes sense that scientists grouped the hippos with the pigs; they share a four-toed ungulate foot, stubby legs, and a barrel-chested build. For years, the accepted theory, based on the fossil evidence, was that hippos were in fact a sub-group of pigs.

As it happens, however, DNA shows that hippos and pigs aren’t even all that closely related (hippos are closer relatives of giraffes than pigs).

At some point in the very distant past, first camels (likewise even-toed ungulates), then pigs split away from other hooved creatures, forming their own branches on the evolutionary tree. Then, around 59-60 million years ago, great-great-(100,000 more greats)-grandpa hippo-whale split off again, parting ways with the branch that would become modern-day ruminants (a large group comprised of most of the remaining hooved animals, including cattle, deer, giraffes, and antelopes). After a few million years together, hippos and whales eventually split up around 54 million years ago; each group started spinning off multiple variations, the vast majority of which went extinct many, many years back.

Over millenia, whale ancestors’ feet morphed into fins (and eventually the back legs disappeared entirely), their bodies elongated and streamlined, and their musculature evolved to propel them through the sea. But despite some very apparent differences, hippos and whales still share some curious features rarely seen in other mammals.

The first is their strangely similar stomachs. Ruminants are defined by multi-chamber stomachs; they regurgitate food at least once, chew the cud, and swallow again, extracting more nutrients. Carnivores, on the other hand, have a single stomach; food is broken down chemically (as opposed to mechanically, as in the ruminants) and excreted in a single process.

Hippo stomachs are a strange hybrid; the animals don’t regurgitate food, but they do have two “preliminary” chambers, their walls roughly textured to help break down the food, which act almost as an internal compost bin; the stomach is so large, and includes so many pockets and chambers, that food is given a chance to ferment before passing to the final, “true” stomach (which resembles the stomach of a carnivore). For years, biologists couldn’t figure out why whales—most of them carnivorous—had multi-chambered “grazer” stomachs, too. The discovery of the link between whale and hippo DNA, points to the whale’s terrestrial history, explains this longtime mystery!

As inexplicable as the whales’ land-lubbing stomachs are the hippo’s undersea-oriented lungs. Most terrestrial animals, including humans, have multi-lobed lungs, but aquatic mammals have single, non-lobed lungs; these can fill with air, or expel it, much more rapidly, allowing animals to surface only briefly in order to “refill.” While hippos do spend plenty of time in the water, it was unclear why a pig descendant would first evolve lobed lungs, then re-evolve single-sac lungs. Much more reasonable is the assumption that an aquatic or semi-aquatic hippo ancestor with non-lobed lungs simply evolved to be even better-suited to the water (in the case of the whales).

Still not convinced? There’s still one very vocal piece of evidence: the hippo’s massive, strangely oriented larynx.

In mammals, the size of the voice-box corresponds to the sounds it can make; bigger larynxes can boom out bass-range sounds, tiny ones are great for treble. In hippos, not only are the larynxes disproportionately large, they’re oriented at a different angle than most terrestrial animals, in a way that matches whales’ voice boxes, and which is thought to help transmit the sounds into the water. Hippos have also been known to produce clicking sounds that resemble those made by orcas; it’s thought that most of their communication in fact occurs underwater.

Considering the weighty evidence (and the similarity in size), maybe the hippopotamus needs a new name. “Cetosedaphos,” a combination of ketos and edafos, sounds about right to us; that would be (approximate) Greek for the “land whale” we’ve come to know as a hippo!

Thinking about going on an African safari? Your trip will deliver memories to cherish for a lifetime. As you begin planning your African adventure, take a look at the following eco-friendly and socially responsible travel tips to help you become more familiar with local customs and to help you tread lightly on the land during your visit. Safari njema!

Feel free to add your comments section below, and make sure to share these tips with fellow travelers on Facebook and Twitter!

The spectacle of a cheetah running at full speed is art; the anatomy and physique facilitating its speed and agility is genetic engineering at its best. The cheetah can accelerate from 0 – 60 mph in 3 seconds, making it the fastest land animal on the planet. Yes, even faster than Usain Bolt. Like Bolt, the cheetah is a sprinter – not a long distance runner – and can only attain high speeds in short bursts due to the tremendous drain on its energy resources. It could take up to 30 minutes for a cheetah to recover from a chase.

So just how can this big cat accelerate faster than a Ferrari? On the exterior, the cheetah is the most slender of the big cats; its lightweight body (weighing about 80-140 lbs.), small head and long legs are designed for aerodynamics. Structurally, the cheetah has a unique, flexible spine, which allows for extreme flexion and extension while running at top speeds. In spine flexion, when the cat’s legs are directly underneath its body, the scapula and hip are able to rotate to such an extreme angle that the cheetah’s front and hind legs overlap. To reach extension, the spine recoils like a spring propelling the cheetah’s legs out; it is this portion of the gait where the cheetah is able to reach strides up to 25 feet. Lastly, the cheetah is equipped with blunt, semi-retractable claws, which function similarly to soccer cleats. Since its claws never fully retract, like other big cats, they are always at-the-ready to provide powerful traction to the ground.

Watch this new National Geographic video for the pure, stunning beauty of a cheetah running at top speed.
[youtube width=”853″ height=”480″]http://www.youtube.com/watch?v=THA_5cqAfCQ?rel=0[/youtube]

Observing the cheetah’s gait in slow motion makes the dynamics of the flexible spine easily detectable. You’ll notice that only one foot at time makes contact with the ground all the while, the cheetah’s gaze is unfaltering – it is locked and loaded on its prey. See the claws? Unlike other big cats, they only partially retract. Watch all the way through for bonus behind-the-scenes footage.

Being built for speed comes at a price in the bush. Their lightweight bodies and blunt claws are no match for the strength and aggression of others predators such as lions or leopards. If faced to defend itself or its kill, a cheetah would utilize the flight defense instead of fighting. This is one of the many factors challenging female cheetahs, who raise their cubs on their own. Only 10% of cheetah cubs raised in the Serengeti survive to maturity due to the dense population of predators.

Like other wildlife, cheetahs are facing obstacles such as habitat loss and human conflict. Conservation efforts like the Big Cat Initiative and National Geographic launched the Cause an Uproar campaign to help big cats around the world. Tune in to Nat Geo Wild to catch the beginning of Big Cat Week on Sunday, December 9.

Thomson Safaris

Founded in 1981 and based in Watertown Massachusetts, Thomson Safaris has been handcrafting trips-of-a-lifetime for over 35 years. Tanzania is our only destination, and has truly become our second home. We’re excited to be able to share it with you through stories and features on our blog.